There have been different techniques for monitoring wastewater flowing in manholes. For example, reference may be made to the following U.S. Pat. Nos. 4,022,059, 4,058,011; 4,095,466; 4,125,020; and 4,145,926. It is apparent from the foregoing patents that it is important periodically to take samples of and to measure flow rates of wastewater flowing in sewer lines via manholes to determine water quality. In this regard, the flow rate is measured, and samples are taken so that they can be analyzed in laboratories to determine whether or not acceptable levels of impurities are contained therein. In this regard, governmental agencies and others have monitored the water quality of wastewater flowing from industrial plants or the like.
In order to gain access to the wastewater flowing in the manhole for monitoring purposes, personnel have entered the manhole via the manhole opening to position flow sampling probes adjacent to a primary measuring device, such as a weir or a flume at the bottom of the manhole thereof. Personnel must first inspect visually the primary measuring device when it is a weir to characterize it. In this regard, the weir includes a V-shaped notch in the upper edge thereof, and the angle thereof must be determined to calibrate the monitoring equipment. The equipment is then mounted in the manhole near the opening thereof. The monitoring operation is employed continuously for certain intervals of time, such as one week, to take water samples and to record flow rates for the wastewater flowing from a given plant. After the time interval, the equipment is removed from the manhole and moved to another manhole for monitoring wastewater from another plant or the like.
While such methods and apparatus have been satisfactory for some applications, it has been a very difficult and dangerous task for requiring personnel to enter the manhole in view of the high flow rates and the very unsanitary and unpleasant conditions found therein. The manhole and its opening is usually confined to a space only sufficiently large to accommodate a person installing the equipment, and thus the person has very little room in which to work. Also, manholes are subject to flash flooding, and thus the installation procedure is treacherous.
Moreover, while the monitoring equipment disposed within the manhole well is inconspicuous since the manhole cover conceals its presence, the unattended automatic equipment can be tampered with in an unauthorized manner by vandals or by those desiring to cause the equipment to provide erroneous information. Thus, it would be highly desirable to monitor wastewater flowing through a manhole without requiring personnel to enter the manhole. Also, it would be highly desirable to enable the wastewater to be monitored in a secure manner by preventing or at least deterring greatly the access to the manitoring equipment by unauthorized persons, once the equipment is installed in place.